Electrothermal bimorph microactuators provide large displacement at low voltages. Several electrothermal bimorph MEMS (microelectromechanical system) designs utilize a SiO2 thin film as an active bimorph layer and for thermal isolation. However, the brittle nature of SiO2 makes the micromirrors susceptible to impact failure. Additionally the low diffusivity of SiO2 makes the thermal response slow.
Several metal-polymer based thermal bimorph actuators have been explored. For these devices, the polymer layer is much thicker than the metal layer because polymers have the lowest Young's modulus among MEMS materials. Since metals have a much higher thermal diffusivity than polymers, the thermal response of bimorph actuators is mainly determined by thermal diffusivity of the polymer. Typically, MEMS polymers have very low thermal diffusivity (˜10−7 m2/s), which makes the thermal response slow.
Accordingly, there continues to be a need in the art for improved MEMS devices that are less susceptible to impact failure and that show fast thermal response.